Spiral “Archimedes screw” molecule between gold electrodes acts as an electrically driven nanoscale motor
An international team at Israel’s Weizmann Institute of Science, Denmark’s University of Copenhagen, and Germany’s University of Augsburg has built a molecular motor modeled on Archimedes’ screw, the nearly 2,000-year-old device that lifted water uphill. The modern version is a spiral-shaped organic molecule held between two anatomically sharp gold electrodes; an electric current through the structure produces controlled rotation, and reversing the applied voltage reverses the spin.
Copenhagen chemist Michael Pittelkow, whose laboratory works on organic synthesis, physical organic chemistry, and chirality, designed and synthesized the spiral. Weizmann researchers then placed it between the gold contacts. Electrons passing through the helix transfer angular momentum to the molecule, so it turns much as wind turns a turbine. Conductivity rose sharply during rotation—by as much as 100 times in some configurations. Quantum mechanical simulations led at the University of Augsburg indicate that, in those arrangements, the rotating molecule conducts electricity far more efficiently than when it is stationary.
Theoretical physicist Fabian Pauly, a co-author of the study, said the work shows that current can generate directed rotation and that this rotation, in turn, controls the current—pointing toward electrically driven machines at molecular scales.
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